20(S)-camptothecin (CPT), a plant alkaloid, was found to have anticancer activity in 1966 (Wall, M., Wani, M. C., Cooke, C. E., Palmer, K. H., McPhail, A. T. and Slim, G. A. "Plant antitumor agents. I. The isolation and structure of camptothecin, a novel alkaloidal leukemia and tumor inhibitor from Camptotheca acuminata", J. Am. Chem. Soc. 88: 3888-3890, 1966).
During the sixties and seventies the sodium salt of CPT was derived from CPT, and clinical trials of this chemically altered CPT were carried out and then abandoned because of the high toxicity and low potency of this compound (Gottlieb, J. A., Guarino, A. M., Call, J. B., Oliverio, V. T. and Block, J. B. "Preliminary pharmacological and clinical evaluation of camptothecin sodium salt (NSC 100880)", Cancer Chemother. Rep. 54: 461-470; 1979; Muggia, F. M., Creaven, P. J., Hansen, H. H., Cohen, M. N. and Selawry, D. S. "Phase I clinical trials of weekly and daily treatment with camptothecin (NSC 100880). Correlation with clinical studies." Cancer Chemother. Rep. 56: 515-521; 1972; Gottlieb, J. A. and Luce, J. K. "Treatment of malignant melanoma with camptothecin (NSC 100880)." Cancer Chemother. Rep. 56: 103-105; 1972; and Moertel, C. G., Schutt, A. J., Reitemeier, R. J. and Hahn, R. G. "Phase II study of camptothecin (NSC 100880) in the treatment of advanced gastrointestinal cancer." Cancer Chemother. Rep. 56: 95-101; 1972. All these trials were conducted using the hydrosoluble, sodium salt derivative of CPT (CPT Na+), which was administered via i.v. The research of the present inventors has fully confirmed the ineffectiveness and the toxicity of CPT Na+.
Experiments have demonstrated that the non-water soluble CPT is nontoxic and highly effective as an anticancer agent. Furthermore, the present inventors have demonstrated that the intramuscular and oral administration provide unexpectedly better results than the intravenous administration.
Drug therapies have been evaluated with respect to treating human cancer, e.g., human cancer xenograft lines. Human tumors are serially heterotransplanted into immunodeficient, so-called "nude" mice, and the mice then tested for their responsiveness to a specific drug. (Giovanella, B. C., et al., Cancer 52(7):1146 (1983)). The data obtained in these studies strongly support the validity of heterotransplanted human tumors into immunodeficient mammals, such as nude mice, as a predictive model for testing the effectiveness of anticancer agents.
It was determined that 9-Amino-20(S)-Camptothecin (9AC) and 10,11-Methylendioxy-20(S)-Camptothecin (10,11MD) are capable of having high anticancer activity against human colon cancer xenografts (Giovanella, B. C., Wall, M. E., Wani, M. C., Nicholas, A. W., Liu, L. F., Silber, R. and Potmesil, M. "Highly effective topoisomerase-I targeted chemotherapy of human colon cancer in xenografts." Science 246: 1046-1048; 1989). After this finding, the present inventors extended these studies to other human cancers growing as xenografts in nude mice as well as conducted studies on the administration of CPT and its derivatives. It is important to note that the fundamental difference between the chemical used by the present invention (CPT) and the one used ineffectively and with high attendant toxicity in the past (CPT Na+) is that CPT is water-insoluble and CPT Na+ is water-soluble.